Focused Rory McIlroy believes it is imperative to start with an under-par round today at Augusta - if he is to stand a chance of winning this year's Masters and a magnificent career Grand Slam.

For the past 11 years, the eventual Masters champion has been inside the top 10 after the first round, with Tiger Woods the last player to come from well off the pace to claim a green jacket in 2005.

McIlroy's best opening round in eight appearances was the 65 in 2011 which seemed to have set him up for a memorable victory, only for his four-shot lead to disappear with a closing 80.

Since then, the 27-year-old Ulsterman has failed to break 70 on the opening day and his best finish of fourth in 2015 was thanks to closing rounds of 68 and 66, which still left him six adrift of runaway winner Jordan Spieth.

"I think it's always important to get off to a decent start in tournaments, but I think especially here you don't want to feel like you're playing catch-up on this golf course," said McIlroy, who will tee-off at 6.41pm (BST) in the first round.

"You don't need to come out and shoot 65 on the first day, but at the same time you're better off shooting something under par just to get yourself off to a nice start."

Meanwhile, world number one and tournament favourite Dustin Johnson is a serious doubt for the Masters after injuring his back in a "serious fall" last night, his agent has said.